Logic in Fuzzy Tree Fragments

To help you work with enhanced FTFs,
ICECUP 3.1 has a vastly enhanced FTF editor interface. One
of its key elements is a floating ‘edit node’ window.

Below you can see just the options for editing the function and
category elements in a single FTF node.

Using this set of options, called Func:Cats, alone you can
say that the node may match one of a set of possible categories
(N v PRON) or cannot possess a particular function (¬NPHD).
The window shows the set of functions and categories compatible
with its complement.

The edit node window has two other ‘tabs’: Features
and Logic.

With the Features tab you can allow a node to match any
set of alternative features. You can mark a feature class as unspecified
(useful in formal experiments), or individually negate any feature
(to say ‘CL(~ditr)’ for example).

The Node Logic Editor

You can also edit any logical combination of patterns using the
Node Logic editor. This is built into the Logic tab.

With this editor you can manipulate any propositional expression
of node patterns. For example, you can specify that a node in an
FTF may not match a particular pattern or may match one or
other of two (or more) patterns, as shown below. (You can combine
node patterns with and although this is usually less useful.)

The following diagram shows the Edit Node window with the logic
editor enabled.

The currently selected node pattern is reflected in the other controls
above the tabs.

To edit a pattern, you can either use these pull-down controls
or select another tab and then flip back to the logic editor. To
edit the overall logical expression you can click on the buttons
below the tab or use the keyboard.

The simplify option, shown as a light bulb, applies logical reasoning
to draw out the implications of the expression. This can be useful
in preventing your expressions from becoming too convoluted!